The marbled crayfish, (Marmorkrebs) Procambarus sp., inhabits freshwater habitats in Germany and the Netherlands, and it is the only known parthenogenic crayfish species. It is widely available in pet stores. The goal of this study was to better understand some aspects of embryogenesis of the marbled crayfish, specifically, morphomechanical properties of the egg. We found that 1.) the duration of marbled crayfish embryogenesis is 462 degree days (D°) at 22ºC, 2.) the volume of eggs at 100 D° is 2.11 ± 0.12 mm³ and it increases to 2.39 ± 0.12 mm³ shortly before juveniles hatch, 3.) egg membrane resistance at 100 D° is 173 ± 0.65 g, but declines to 1229 ± 0.78 g shortly before hatching, 4.) the nauplius stage appears at 132 D°, and 5.) heart activity is observed after 240 D°. This species parthenogenic ability, high fecundity, possibility of multiple clutches during the year, and high tolerance to potentially harmful environmental factors make this species a serious threat to the native European crayfish fauna. Therefore, it is important to understand and to educate people about the potential hazard that marbled crayfish pose once released into the environment. It is especially important to inform amateur aquarists, who maintain these crayfish in decorative home aquaria, about the threats they pose.

Submissions to JCB are up; we have a wider array of authors from an increasing number of countries across the globe; we are recording increasing number of hits in BioOne to JCB articles as evidenced by a rise in income from BioOne and JSTOR; our impact factor is rising. In other words, people are using JCB!

Now the bad news:

However, while we continue to move JCB into the digital age, our membership in The Crustacean Society (TCS) has been slipping away. Sad to say, in 2010, for the first time TCS ran a deficit. There appears to be a curious disconnect. Because of the internet, use and access to the JCB are up. But people do not seem to realize that if we do not have enough TCS members, there will not be a journal.

Sometimes people ask what they get from scientific societies. High quality journals at a reasonable price compared to for profit publishers is a major one. If you do research with crustaceans, consider joining the Society!

19 January 2011

Back in July, I mentioned one the the day’s highlights from the International Association of Astacology conference:

getting introduced to the first new crayfish species in a decade (and a big one)

That new species has been formally published, and its name is Barbicambarus simmonsi. And quite handsome it is, too:

New Scientist has a short article about the new species (registration may be required), emphasizing its size. I recall that when Chris Taylor gave his talk at IAA, his colleagues were asking locals if they knew about any crayfish in the area. People said no, “but there were some big lobsters upstream.”

This emphasizes yet again how much undiscovered biodiversity there is in North America, the hotbed of crayfish. We’re still finding new species that are physically large in not particularly obscure habitats. But as this is the first new crayfish species described in a long time, it may be one of the last “low hanging fruits”; other new crayfish may be either very similar to others morphologically, or live in isolated environments like caves.

This species also seems to be rare, which points out the need for conservation and monitoring.

Additional: A Reuters wire story on this discovery is making the rounds. It’s great to see that crayfish and basic taxonomy making the news. This article has a nice picture comparing the size of the new species to another in the same region.

More additional: A longer write-up of the discovery can be found in the university press release.

Most people are shocked to learn that there are about 600 species of crayfish in the world, Taylor said, with more than half of those occurring north of Mexico. Alabama and Tennessee are hotspots of crayfish diversity, he said.

The discovery of a new species of crayfish in itself is not unusual, the researchers said. About two new species of crayfish are found every year in the U.S. But the discovery of a large, distinctive new species in a region that had been studied for decades is quite astounding, they said.

Reference

Taylor CA, Schuster GA. 2010. Monotypic no more, a description of a new crayfish of the genus Barbicambarus Hobbs, 1969 (Decapoda: Cambaridae) from the Tennessee River drainage using morphology and molecules. Proceedings of the Biological Society of Washington123: 324-334. http://dx.doi.org/10.2988/10-15.1

18 January 2011

For a project I was working on, I had reason to compile the county records of crayfish contained in the very good and useful book Texas Crawdads (self-published, but still available for purchase online). The book shows a map with all the Texas counties that have crayfish, but I wanted to see the biodiversity “hotspots.” Because the book has county maps for most of the species, I was able to extract the information from them and compile it into a quick and dirty choropleth map:

The county with the most species, Brazoria, has ten different crayfish species. Van Zandt county (the one white patch in the north east) is shown in a summary map as having a crayfish record, but none of the genus or species maps show anything there.

This map underestimates the number of crayfish species in some counties, particularly in North and West Texas. There are seven (out of 39) species that the authors don’t give county maps for, though where they do mention specific counties in the text, I put that in my spreadsheet).

In particular, there are two very wide-ranging gray crayfish, Procambarus curdi and P. simulans, that didn’t warrant their own county maps, just a combined map with a third species (which did get its own separate map). P. simulans is described as having the widest distribution, so every county that is shown in Texas Crawdads as having “grays” with is assumed to have P. simulans. Those entries are marked with an asterisk.

What does this have to do with Marmorkrebs? It’s sort of related to a paper that’s in press right now about potential distribution of Marmorkrebs in the United States and elsewhere. But mainly, I just wanted to share the compilation in case someone else finds it useful.

11 January 2011

Marmorkrebs make a brief cameo appearance in this article in New Scientist on the importance of variation in evolution. It’s behind a registration wall, unfortunately, and will disappear to a “subscribers only” section in a few days, so catch it while you can. But here’s the relevant excerpt:

Is this “uncertainty hypothesis” right? There is evidence that epigenetic changes, as opposed to genetic mutations or environmental factors, are responsible for a lot of variation in the characteristics of organisms. The marbled crayfish, for instance, shows a surprising variation in coloration, growth, lifespan, behaviour and other traits even when genetically identical animals are reared in identical conditions. And a study last year found substantial epigenetic differences between genetically identical human twins. On the basis of their findings, the researchers speculated that random epigenetic variations are actually “much more important” than environmental factors when it comes to explaining the differences between twins (Nature Genetics, vol 41, p 240).

The German site Aqua4you has an article about Marmorkrebs that seems to be contain good basic information on caring for Marmorkrebs as pets. I say “seems to,” because I am relying on Google Translate to tell me most of what it says. Maybe that’s why the family is being shown as “invertebrate / amphibian”... though I doubt it. It’s a rather odd grouping. I guess the classification is, “lives in an aquarium but isn’t a fish.”

I thank Jason Gold and his team of editors for all their hard work, turning out this set of selections in record time! Also thanks to all those who blogged, submitted posts, and congratulations to all those who entries made it in.